Telegraph key



C. A. HART TELEGRAPH KEY Jan. 10, 1939.

Filed July 8, 1936 2 Sheets-Sheet 1 C. A. HART TELEGRAPH KEY Jan. 10, 1939.

Filed July 8, 1956 2 Sheets-Sheet 2 mum I nventor Patented Jan. 10, 1939 PATENT OFFICE TELEGRAPH KEY Clyde A. Hart,

Richmond, Ind.

Application July. 8, 1936, Serial No'; 89,604

11 Claims.

This invention relates to the class of telegraphy and pertains particularly to an improved dual type of telegraph key. The primary object of the present invention is to provide a manually operated dual telegraph key which is-so designed that it is possible in sending code to accurately space dots and dashes by reasonof the provision of spring sup-ported key actuated contacts in which the ratio of the period of vibration of the contact carrying springs is one totwo, thereby making it'possible to automatically add to the dot signal formed by the vibration of one spring on movement of the associate key, two dot signals from the vibration of the other spring when its key is actuated to produce a closed circuit signal period equal to three dots or one dash.

Another object of the invention is to provide in a dual key code transmitting instrument of the above described charactena novel'means for increasing or decreasing the effective sending speed of the instrument without changing the period of vibration ratio between the contact carrying springs which are set vibrating upon the actuation of the keys.

A still further object of the invention is to provide in an instrument of the above described character in which is'employed the two contact carrying springs, a-novel means for changing the vibration frequency of one spring relative to. the other whereby the said two to one ratio maybe maintained between the springs as the springs lose their resiliency through use;

A still further object of the invention is to provide an instrument of the character defined for sending messages indot and dash code, by'which such sending is not only rendered less laborious, but may be completely accurate and more nearly perfect in the sense that the receiver may clearly distinguish dots from dashes.

Another important object of the invention is to provide telegraph key means of the character indicated above which insures that the dashes be exactly'three times the length of: the dots, so as to eliminate confusion at the receiving station.

Other important objects of my invention will be apparent from a reading of the following description taken in connection with the drawings, wherein for purposes of illustration I have shown a preferred embodiment of my invention.

In the drawings:-

Figure 1 is a general top plan view of the embodiment.

Figure 2 is a side elevation view.

Figure 3 is a transverse vertical sectional view;

Figure 4 is an enlarged side elevational view of a portion of the mechanism.

Figure 5 is a top plan view of portions ofthe pivoted key arms showing the spring inserts therein.

Figure 6 is aside elevational view of one of the posts.

Figure 7 is a transverse vertical sectional view taken through the right hand end of the upper arm appearing in Figure 1 and looking toward the right.

Figure 8 is a diagram showing the amplitude of the swing of the arm 40.

Figure 9 is a diagram showing the amplitude of the swing of the arm 4i.

Figure 10' is a diagramwith a legend showing the relative lengths or widths of the signal elements as described by arms 40 and 4'! in their operation and the resultants of these signal elements and their relative spacing.

Referring in detail to the drawings, the numeral 5- generally designates a suitable base adjacent one end'of which is mounted the U-shaped bracket which is generally designated 6 and which includes the L-shaped bracket member 1, the oppositely' projecting dual stop support 8, and the opposite side stopsupports 9 and 10 which are acutely angulated and carry at their outer extremities the adjustable stops H and I2 arranged to be engaged by the acutely angulated portions l3 and 14 of the respective swingable key arms [5 and 15 which are pivoted on the pivot H. The acutely angulated portions l3 and I4 being crossed extend beyond the common pivot ii to opposite sides of their original positions and there merge with respective parallel portions l9 and which have attached thereto the dielectric fanshaped finger grips 2| and 22.

The portion l9 has thereon the adjustable contact 23 for engaging the contact post 24 which projects upwardly from the base and has the wire 25 connected thereto which leads to the binding post 26. The binding post 26 is connected by a wire 21 with the terminal fixture which is generally designated 28, as clearly appears in'Figure 1 of the drawings.

Each of the portions l9 and 20 has longitudinally inwardly of the contact 23 the adjustable posts 29 and 30 which have attached to their inner ends helical springs 31 and 32 which springs have their opposite ends connected to the left hand extremity of the stationary bracket 1, whereby the normal position of the swingable key arms l5 and I6 is one in which the parallel portions of the arms are substantially in parallelism with the stop supports 1 and 8-.

The stop support 8 has acutely angulated portions 33 and 34 which are substantially parallel to the angulated. portions l3 and M of the swingable key arms and the extremities of these portions 33 and 34 carry adjustable stops 35 and 36 which are in opposition to the stops H and I2 and are adapted to be engaged by the angulated portions 13 and I4 of the swingable arms under conditions which will be pointed out hereinafter.

By referring to Fig. 5 it will appear that the swingable arm I5 has its parallel portion 31 shorter than the corresponding parallel portion 38 of the arm I6 and that a spring insert 39 which connects the farther parallel portion 40 with the parallel portion 31 is longer than the corresponding spring insert 42 which connects the portions 38 and 4| of the arm I6. Further, there is mounted on the arm I5 the adjusting structure which is shown in detail in Figure 4 and which comprises the vertically elongated member 43 which extends equally above and below the portion 31 of the arm I5 and is fastened thereto by rivets or the like 44. A similarly shaped member 45 is secured by screws 41 and 48 to the spring portion 39 of the arm I5, and engages opposite sides of the spring 39 thereby holding the spring and determining the length left free for vibration. It will be understood that the arm portions I3, 31 and I4, 38 as well as th arm portions 40 and 4| are rigid.

Threaded through the body 45 is the threaded end of an adjusting bolt 49 which has a smooth portion 50 slidable through a receiving opening in the upper end of the body 43; while another bolt 52 has a threaded portion threaded in the lower part of the body 43 and a smooth portion 5| slidably mounted in a receiving opening in the lower end of the body 45. The bolt 52 has a. head 53' which engages the left hand side of the lower part of the body 43. Penetrating the upper part of the body 45 is the screw 49 for engaging and locking the upper bolt 49 in adjustment. Another screw 52' traverses the lower part of the body 45 for locking the bolt 52 in adjustment.

The portions 49 and 4| of the arms I5 and I6, respectively, are rigid like the portions 37 and 38 and extend normally in parallel positions as illustrated in Figure 1 of the drawings on opposite sides of the terminal fixture 28, the latter consisting of a vertically projecting block 53 with the adjustable contact 54 pointing toward the arm I6 and the adjustable contact 55 pointing toward the contact arm I5. The block 53 is insulated from the base 5.

On the contact arm portion 40 of the contact arm I5 is the V-shaped spring 56 with a contact head 51 normally spaced from the contact 55. The portion 4| of the arm I6 has a corresponding V-shaped spring 58 with the contact head 59 opposed to the end of the adjustable contact 54.

The bars or outer portions 49 and 4| of the key actuated arms I5 and I6 are provided with pins 60 and 6|, as shown in Figure 1, as position indicators for the slidable weights 62 and 63 so that such weights may be shifted on the bars to increase or decrease the rapidity of vibration of the bars 46 and 4| and to increase or decrease the movements of the contacts 51 and 59 relative to the contact screws 54 and 55, without changing the vibration ratio of the springs to one another. These weights 62 and 63 are provided with set screws 63' and 64 by which they are locked in adjusted positions on the supporting bars and the weights are provided with suitable slots to enable them to pass the position indicating pins when it is necessary to make adjustments involving the movement of the weights past the pins.

It is to be noted that the terminal fixture 28 is insulated from the base 5 as are the elements 24, 26 and 28 and the wires 25 and 27. In view of this arrangement the binding post 26' is connected in electrical engagement with the base 5 While the binding post 26 is insulated from the base and carries one side of the current from the contact 24 to the fixture 28 by means of the wires 25 and 21 already described, which wires are insulated from the base 5 and all other parts of the instrument.

The numerals 65 and 66 designate respective bumpers which are adapted to be engaged by the arms I5 and I6 and whose purpose is to absorb the vibration and stop the arms after ceasing sending operations.

The adjustment, proportioning, and operation of the parts described above is as follows:

In Figure l, the portion I8 on the arm I5 has two bolts I8 and I9. The bolt I9 nearest pivotal point I'I acts as a pivot for the arm I9 and fingergrip 2| when the bolt I8 nearest fingergrip is removed whereat the bolt 23 may be carried and held against contact 24 for any desired length of time, by pushing the finger-grip 2| inwardly, enabling the operator to make a continuous signal for the purpose of tuning a transmitter or receiver. I wish to make clear the fact that the provision for breaking the arm I5 at the point I8 does not, in any way, effect the operation of the key and that in normal operation of the key bolt 23, the contact 24 and portion I8 are not utilized, but could be left out entirely without eifecting the basic principle of the key, which I shall explain.

The pairs of pegs 60 and 6| are placed on arm portions 49 and 4| in such positions that when weights 62 and 63 are placed on the arm portions 40 and 4| next to relatively opposite pegs 60 and GI, the arm portion 40, by virtue of the longer spring 39 will vibrate at one-half the speed of the arm portion 4| when the arms I5 and I6 are put into operation by pushing finger-tips 2| and 22 inwardly toward each other.

In ordinary operation of the key, when the operator wishes to change the speed of sending, he simply moves the weights 62 and 63 on the arm portions 40 and 4| to another pair of pegs 60 and 6|.

The object of the compensating device illustrated in Figures 3 and 4 is as follows:

Through use and strain the springs 39 and 42 may lose their original tension characteristics, in which event the arm portions 40 and 4| would not vibrate at their required relative speeds.

To correct for this loss of original tension characteristics, the operator starts arms 49 and 4| vibrating. He then may loosen the screws 41 and 48 slightly, if necessary, to permit movement of the bar 45 longitudinally of the spring and then turns the screw 49 so as to cause the bar 45 to be shifted lengthwise of the spring until a position is reached where the holding action of the screws 4'! and 48 on the spring will cause it to vibrate at one-half the speed of the arm portion 4|, thereby making perfect dashes. The screws 41 and 48 may then be made perfectly tight against the two sides of the spring so that it will continue to oscillate at the desired speed. The operator knows when the key is creating perfect dashes by listening to the created signal,

The positioning of the body 45 and the point of engagement of bolts 41 and 48 relative to spring 39 virtually lengthen or shorten the spring 39 as far as its natural rate of vibration is concerned.

When the key is not in use, the angulated portions I3 and I4 of the arms I5 and I6 engage the stops II and I2 of the portions 9 and I8; and the extreme right hand ends of the arms 40 and 41 engage the bufers 65 and' 661 These positions of the arms |5 and IG- are maintained by the-force exerted by the helical springs 3|- and 32 against the screws 29' and 30 urging them and the portions l9 and 20 laterally outwardly until the portionsl3 and |4engage the-stops Hand [2.

To create signals the bindingpost's 2'6-and 26a are connected electrically-to a suitable signal generator (not shown).

To create a dash ordashes; the finger-grips and 2-2- are moved laterally inwardly until'inthat position, thereby causing the portions I 9- and 20,

I3" and M 31 and 38, shown in- Figure 5; the

springs 39 and- 42, the arms 40 and' 4|, the- V- shaped springs 55 and- 58; and the contacts 5-! and 59 to move laterally inwardly until the angulated portions l3 and engage the-stops 35' and 35 of part 8. 7

These positions of arms l5 and I6 are maintained and the forcecreated by the moving of the arms l5 and I6 from their initial or idlepositions causes the arms 4|! and 41 to vibrate, becauseof the action of the springs Hand 42, and this vibration causes the contacts 51 and 55 to periodically engage with and disengage from the screws 55 and 54, respectively, of block 53, thereby mechanically and electrically creating dashes during the engagement and establishing spaces during the disengagement; because of the fact that one side of the electrical circuit is carried by the contacts 51 and 59 and the" other side of the electrical circuit is carried by' the screws 55 and 54.

Due to the fact that the arm 40'vibrates at onehalf the speed of the arm 4|, because of the rela-- tive lengths of the springs 39 and 42, the periods of engagement and disengagement of the-contact 51 and the screw 55'will be of twicethe length of those of the contact 59 and'screw 54, as will be the length of the signals created and the spaces allowed.

However, because" of the arrangement stated, the two signals are additivel'y created and the combined or resulting signal is one continuous unit of three times the length of the signalcreated by the engagement of the contact 59 with the screw 54 alone; and constitutes a dash. The length of the intervening space is that allowed by the disengagement of the contact 59 and the screw 54. This entire action is clearly illustrated in Figures 8, 9 and 10 of the-drawings.

Any number of consecutive, uniform dashes, within the scope of the telegraphic'codes, may be created automatically and uniform spaces between dashes allowed automatically, so long as the finger-grips 2| and 22 are" held inwardly.

To cease the making of dashes, the finger-grips 2| and 22 are released, so as to permit the helical springs 3| and 32 to expand and return the arms I5 and I6 to their initial or idle positions. The buffers 65 and 6B absorb any remaining'momentum in the arms 40 and 4 I.

To create dots only, the arm I5 is put into operation by moving the'finger-grip 22'laterally inwardly and holding it in that position so as to cause the arm 4| to vibrate and produce periodic engagement and disengagement of the contact 59 with the screw 54, mechanically and electrically.

Any number of dots may be created, within the scope of the telegraphic codes, in this manner, so long as the finger-grip 22' is held in the described laterally inward position.

To cease the creating ofdots, the finger-grip 22 is released, so as toperm-it the helical-spring 32 to expandl and return the: arm 16- to its initial idle position. The bufier 66 absorbs any remaining momentum in the arm 4| so that it is quickly brought to rest.

The operation and advantages of the key are as follows: as shown'in' Figures 8 and. 9.

The arm portion 4| vibrating as it does at twice the speed of the arm portion 40, describes an arc one-half the size described by the vibrationof the armportion 40.

When the arm portion 4|! swings through A- BA contact is made between the bolt 55 and contact spring 56 and a signal is heard. When the arm portion 48' swings through A--C--A no contactis-made and a space is made.

The same action is true of the arm portion 4|. As a result of movement through DE-D, bolt 54 and the spring 53 make contact and a signal is heard. Through-D-F-D, no contact is made so that a space is defined.

Since-the arm portion 40 moves through an are twice as-large as that of the arm portion 4|, the signals and spaces of 40 are oftwice the length of'those-of 4|.

Referring to Figure 10:-

1=arm 4| vibrating alone.

2: arm 40 vibrating alone.

:combined result of arm 40 and 4|, vibrating simultaneously.

To make a dot or dots, the arm portion 4| is made tovibrate' alone by pushing the fingertip 22 inwardly;

To make adash,.both. arm portions 4| and 4| are made-to'vibrate. The arm portion 40 is never operated alone.

The point fl'shown between the diagrams and 2 of Figure 10; is explained. With both arm portionsvibrating, as the arm portion 4|lstops maki-ng contact, the arm portion 4| starts making contact. This action is continuous-and explains why arm portion4ll-must vibrate at exactly onehalf the speed of arm portion 4|. The result of the simultaneous vibration of the arm portions is shown in 31 Since thecontact and signal phase of 40 is equal to two dots (arm 4|) and the arm portion 41' adds another dot, the combined result is a contact and signalequal to three dots, which is a dash.

Bythis arrangement, the spaces of arm portion 4|) (if it were vibrating alone) are halved, leaving a space exactly the length of one dot.

Any number of dashes may be made consecutivelyby'pushing both of the finger-grips toward eachother and holding them thus until the required number of dashes are made.

More accurate sending is accomplished by means of' the invention since the dashes are always equal three dots and the spaces between dashes always equal one dot, this being accomplished automatically without requiring any exerelse of judgment or skill by the operator as required in the operation of an ordinary semi-automatic key;

Since the arm 4| must be vibrating for the creation of' dashes as well as dots, it naturally follows-that arm 4| must start vibrating at the beginning of each andevery code character and is not permitted to cease vibrating untilthe charact'er'is completed.

In view of this fact and the fact that a dash or dashes are created by the combined additive result of the signals created by the vibrations of the arms 40 and 4|, it follows, as illustrated in Figure 10 of the drawings; that there are definite,

critical instants during the creation of any code character composed of dashes or both dots and dashes, for starting and stopping the vibration of the arm 40. If the starting and stopping is executed at incorrect instants, the result will either be overlapping of the two signals created by the arms 40 and 4| causing the combined signal to be shorter than is required; or there will be an intervening space between the two signals and not one continuous unit. In either case the result will not be a dash.

The operator of the key must bear in mind at all times that the arm creating the dots, namely the arm 4|, continues to vibrate while he is executing a dash or dashes and that he is afforded only a certain limited time in which to make the dash or dashes. Thus, of necessity, he must operate the key correctly, which operation implies the creating of perfect code signals.

This requirement for correct operation is in direct contrast with the requirements of operation of the ordinary semi-automatic key which consists of one mechanism for making dots automatically and another separate mechanism for making dashes, not automatically as with my key, but in a manner in which each dash is executed separately and manually.

The semi-automatic type of key demands that the dot making mechanism remain idle during the making of the dashes. For this reason and because each dash is made separately and manually, the lengths of the dashes created and the intervening spaces may not be uniform, due to the faulty judgment of the operator, whereas my key makes dashes and spaces automatically and they are, therefore, of uniform lengths.

Less labor is required for the operation of my key because each dash does not have to be made manually and separately and because the arm creating the dots does not have to be released during the creation of a dash or dashes.

Electrical circuit Referring to Figure 1 of the drawings, the posts 26 and 24, the wires 25 and 21 and the part 28, are all insulated from the base 5. They form one side of the electrical circuit of the key. Current travels from the post 26 through the wire 21 to the block 53 and the screws 54 and 55, and also from the post 26 through the wire 25 to the post 24.

The other side of the electrical circuit includes all of the remaining parts of the key except the finger grips 2| and 22. The current travels from the post 26' through the base 5, the bracket 6, the pivot H, the portions l3 and H, the springs 39' and 42, the arms 40 and 4|, the springs 56 and 58 to the contacts 51 and 59, and also from the post 26 through the base 5, the bracket 6, the pivot H, the portion and to the screw 23.

Although I have shown and described herein a preferred embodiment of my invention, it is to be definitely understood that I do not desire to limit the application of the invention thereto, and any change or changes may be made in the materials, and in the structure and arrangement of the parts, within the spirit of the invention and the scope of the subjoined claims.

What is claimed is:--

1. A telegraph key comprising a base, a pair of complementary relatively swingable arms pivotally supported on said base and arranged for simultaneous and separate operation by hand, a primary contact assembly arranged adjacent the pivotal point of said arms and with which said arms electrically engage as the arms are manipulated, a secondary assembly adjacent the outer ends of said arms and with which the outer ends of said arms engage at certain points in the operation of said arms, said arms having flexible spring portions located intermediate their pivotal points and the said outer ends, said outer ends including compressible spring contact means arranged to actuate said outer ends of the arms after engagement with the corresponding portions of said secondary contact assembly.

2. A telegraph key comprising a base, a pair of complementary relatively swingable arms pivotally supported on said base and arranged for simultaneous and separate operation by hand, a primary contact assembly arranged adjacent the pivotal point of said arms and with which said arms electrically engage as the arms are manipulated, a secondary assembly adjacent the outer ends of said arms and with which the outer ends of said arms engage at certain points in the operation of said arms, said arms having flexible spring portions located intermediate their pivotal points and the said outer ends, said outer ends including compressible spring contact means arranged to actuate said outer ends of the arms after engagement with the corresponding portions of said secondary contact assembly, and buffers for said outer ends of said arms for stabilizing the same after sending operations have been ceased.

3. A telegraph key comprising two key arms pivoted for relative oscillation on vertical axes, said arms being adapted for electrical connection with one side of a signal circuit, means facilitating relative oscillation of said arms, a pair of fixed contacts adapted for electrical connection with the other side of said circuit, a contact finger carried by each arm and normally spaced from a fixed contact, and means forming a part of each arm which is so constructed and arranged that upon movement of said arms said contact fingers will have vibratory engagement With said fixed contacts at a vibration frequency of one to two.

4. A telegraph key comprising two key arms pivoted for relative oscillation on vertical axes, said arms being adapted for electrical connection with one side of a signal circuit, means facilitating relative oscillation of said arms, an elongated spring member constituting a portion of each arm, a contact finger supported from each spring, a pair of fixed contacts adapted for electrical connection with the other side of said circuit and each arranged for engagement by a contact finger, and said springs having a relative vibration period of one to two whereby upon oscillation of said arms one contact finger will automatically electrically engage twice with the contact adjacent thereto while the other finger is electrically engaging once with the other fixed contact.

5. A telegraph key, comprising a pair of pivotally mounted key arms adapted for independent or simultaneous movement, means for electrically connecting said arms with one side of an electric signal circuit, a pair of fixed contacts interposed between relatively movable free ends there of, the other ends of the arms being adapted for manual engagement by an operator, a pair of resilient contact fingers carried by said arms at the said free ends thereof and upon the opposing faces thereof, each of said fingers being positioned for engagement with a contact upon movement of the carrying arm therefor, and a spring forming a part of each arm between the pivot point thereof and the contact finger carried thereby, the springs of said arms having a relative vibration ratio of one to two.

6. A telegraph key, comprising a pair of elongated rigid members, pivotal supporting means therefor facilitating their simultaneous or independent oscillation, finger engaging means upon two adjacent ends of said members, a fiat spring forming a longitudinal continuation of the other end of each member, an electric contact finger supported from the end of each spring remote from the adjacent rigid member and electrically coupled with the member, said members being adapted for electrical contact with one side of a signaling circuit, a pair of fixed contacts each adjacent to a contact finger for electrical engagement thereby upon oscillation of the finger carrying member, said fixed contacts being adapted for electrical connection with the other side of said circuit, and said springs having different oscillation periods whereby upon operative movement of said members the fingers will have vibratory contact with the fixed contacts at a determined periodic ratio.

7. A telegraph key, comprising a pair of elongated rigid members, pivotal supporting means therefor facilitating their simultaneous or independent oscillation, finger engaging means upon two adjacent ends of said members, a flat spring forming a longitudinal continuation of the other end of each member, an electric contact finger supported from the end of each spring remote from the adjacent rigid member and electrically coupled with the member, said members being adapted'for electrical connection with one side of a signaling circuit, a pair of fixed contacts each adjacent to a contact finger for electrical engagement thereby upon oscillation of the finger carrying member, said fixed contacts being adapted for electrical connection with the other side of said circuit, and said springs having different oscillation periods whereby upon operative movement of said members the fingers will have vibratory contact with the fixed contacts at a one-to-two ratio, and means for changing the vibration speed of said springs to change the sending speed of the instrument without changing the vibration ratio between the springs.

8. A telegraph key, comprising a pair of elongated rigid members, pivotal supporting means therefcr facilitating their simultaneous or independent oscillation, finger-engaging means upon two adjacent ends of said members, a flat spring forming a longitudinal continuation of the other end of each member, an electric contact finger supported from the end of each spring remote from the adjacent rigid member and electrically coupled with the member, said members being adapted for electrical connection with one side of a signaling circuit, a pair of fixed contacts each adjacent to a contact finger for electrical engagement thereby upon oscillation of the finger carrying member, said fixed contacts being adapted for electrical connection with the other side of said circuit, said springs having different oscillation periods whereby upon operative movement of said members the fingers will have vibratory contact with the fixed contacts at a one-totwo ratio, a weight member supported by and at the end of each spring adjacent the finger carried thereby, the weights being movable lengthwise of the spring for changing the speed of vibration thereof, and position indicating means for the weights relative to the springs whereby such speed of vibration of the two springs may be changed without changing the one-to-two ratio thereof.

9. A telegraph key, comprising a pair of elongated rigid members, pivotal supporting means therefor facilitating their simultaneous or independent oscillation, finger-engaging means upon two adjacent ends of said members, a fiat spring forming a longitudinal continuation of the other end of each member, an electric contact finger supported from the end of each spring remote from the adjacent rigid member and electrically coupled with the member, said members being adapted for electrical connection with one side of a signaling circuit, a pair of fixed contacts each adjacent to a contact finger for electrical engage ment thereby upon oscillation of the finger carrying member, said fixed contacts being adapted for electrical connection with the other side of said circuit, said springs having different oscillation periods whereby upon operative movement of said members the fingers will have vibratory contact with the fixed contacts at a determined periodic ratio, and means associated with one spring for compensating for inherent changes in the springs affecting the period of vibration thereof whereby the said determined vibration ratio may be maintained.

10. A telegraph key, comprising a pair of elongated rigid members, pivotal supporting means therefor facilitating their simultaneous or independent oscillation, finger-engaging means upon two adjacent ends of said members, a fiat spring forming a longitudinal continuation of the other end of each member, an electric contact finger supported from the end of each spring remote from the adjacent rigid member and electrically coupled with the member, said members being adapted for electrical connection with one side of a signaling circuit, a pair of fixed contacts each adjacent to a contact finger for electrical engagement thereby upon oscillation of the finger carrying member, said fixed contacts being adapted for electrical connection with the other side of said circuit, said springs having difierent oscillation periods whereby upon operative movement of said members the fingers will have vibratory contact with the fixed contacts at a determined periodic ratio, and means for compensating for inherent changes in the springs affecting the period of vibration thereof whereby the said determined vibration ratio may be maintained, comprising a bar secured to one of said members adjacent to the spring carried thereby, means movable on the said last spring for clamping the same to establish an oscillation terminus, and screw means carried by the bar and having threaded connection with said movable means to effect its sliding movement on the spring.

11. In a telegraph key instrument of the type having two pivoted arms each having a finger grip at one end and a contact finger at the other end which is adapted to engage a fixed contact connected with one side of a signal circuit; the improvement which consists in inserting a transversely flexing spring in each arm between the contact finger thereof and the pivot therefor, and one of said springs having a vibration frequency half the vibration frequency of the other spring.

CLYDE A. HART. 

